How does corona ring help against corona discharge? Read on to know about the corona ring guide.
This article will help you learn why does corona ring help against corona discharge. And you can choose corona rings easily for high voltage project.
Corona Ring Help Against Corona Discharge
A corona ring, also known as a shielding corona ring, is a circular conductor, typically made of metal, that is attached to a high-voltage terminal. The primary function of a corona ring is to evenly distribute the electric field gradient and reduce its peak values below the threshold that would cause corona discharge. These rings are commonly used on high-voltage power transmission insulators, switchgear, and scientific equipment that generates high voltages.
Corona discharge occurs when the air around high-voltage conductors becomes ionized, allowing a small amount of current to leak from the conductor into the surrounding air. This phenomenon can sometimes be seen as a faint blue glow near high-voltage equipment. In power transmission systems, corona discharge leads to energy loss, resulting in wasted power. In devices like electrostatic generators, Marx generators, and television sets, corona leakage can lower the output voltage, leading to malfunction. Additionally, coronas generate harmful ozone gas, which can cause deterioration of nearby components such as insulators and pose health risks to workers and residents. Therefore, corona discharge is generally undesirable in electrical systems.
Corona discharge involves the flow of current from the high-voltage electrode into the surrounding air. This can occur in high-voltage power lines and other electrical systems. One effective way to reduce corona discharge is by using corona rings. These rings, made of thick metal rods, are positioned perpendicular to the conductor, with the conductor passing through the ring. The ring is mounted on the power line post and grounded.
The corona ring helps by altering the distribution of the electric field. Instead of allowing current to flow directly from the wire into the air, the corona ring spreads the electric field more evenly around the conductor. This reduces the electric field intensity at any single point, thereby preventing the air from ionizing and stopping corona discharge. The “wire-to-ring” flow is managed in such a way that it prevents the high-field regions necessary for corona formation, effectively suppressing the discharge.
The electric field is redirected to circulate on the ring rather than on the surface of the insulator, which reduces corona discharge.
Is the ring mounted to the power line post and grounded?
Most corona rings are not grounded.
In many cases, insulator stacks have just one corona ring, typically positioned at the line end.
The corona ring at the line end of the insulators is connected directly to the power line, meaning it shares the same high voltage as the power line. This ring is not grounded.
Occasionally, a second corona ring is placed at the grounded end of the insulator stack. This is the only corona ring that is typically grounded.
If, hypothetically, all rings were grounded, the current flow from the wire to the ring would likely be just as problematic, if not worse, than the wire-to-air corona discharge that occurs without the rings.
The key factor is charge density—the ring increases the surface area and radius of curvature, which reduces the charge density. This lower charge density helps prevent significant corona discharge from sharp edges, joints, and other irregularities.
How does a corona ring work?
Corona rings are used to increase the voltage across a component or surface. Corona rings are generally made of aluminum and used in overhead power lines to increase the surface potential and reduce corona loss. These rings are mounted on crossarms.
Corona is an ionized gas occurring naturally in the environment, which can also be produced artificially by high-voltage electrical discharges.
Corona is generally unwanted, especially in electricity transmission where it wastes energy, increases conductor corona loss and radio interference, and can cause damage to insulators. Corona discharge from conductors may also produce ozone (O3) as a pollutant and can cause noise or audible sound.
High voltage corona discharges occur around most high voltage equipment such as power lines and transformers; the electric field strength required for corona depends on air density, moisture content, presence of contaminants or dust, insulation type, shape of the conductor, etc., but is typically 30–40 kV/cm for dry air at sea level pressure (atm).
At lower voltages the air is normally an insulator; however, as voltage increases a stage is reached where small areas of ionization occur and current flows through these paths creating characteristic “streamer” discharges.
Why Wouldn't A Discharge Start Between The Wire And The Ring?
Because the electric field is no longer strong enough to permit an arc or corona discharge.
Corona discharge occurs when the electric field around a conductor is intense enough to ionize the surrounding air, making it conductive. However, since the conductive region doesn’t connect to anything that can complete the circuit and create an arc, a slower movement of ions flows through the neutral air.
By adjusting the electric field, you prevent the air from becoming conductive.
Conclusion
After reading this article, you may learn why does corona ring help against corona discharge. And you can choose corona rings easily for high voltage project.
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